As technology progresses, laser technology in particular is improving and advancing. A mode-locked ultra-short pulse fiber laser may generate a laser with high-peak power and a narrow pulse width, and as a result, the mode-locked ultra-short pulse fiber laser has the properties of wide bandwidth and high power output. Therefore, the mode-locked ultra-short pulse fiber laser may be applied in the surgical operations, fiber communications, frequency measurement, material processing, and other different technical fields.
In the conventional structure of the figure-8 mode-locked ultra-short pulse fiber laser, an isolator may be allocated in the uni-directional loop to isolate the propagation of the reverse laser pulse in the uni-directional loop. Therefore, the reverse laser pulse will be wasted. Therefore, how to make better use of the reverse laser pulse is a subject worthy of discussion.